1. Technical Field
This application relates to sound processing and, more particularly, to controlling the adjustment of a stored background noise estimate.
2. Related Art
In a communication system, signal feedback between a speaker and a microphone may reduce the overall sound quality of the system. Some communication systems attempt to manage feedback by applying various audio processing techniques. For example, a two-way communication system may apply echo cancellation to reduce feedback of speech and noise content. Echo cancellation suppresses far side signal content that has been fed back into the near side microphone. When far side noise content dominates the near side microphone, the signal may be gated to prevent noise feedback. Gating typically applies a large amount of noise suppression to the audio signal. For some types of audio signals, gating may distort the signal and produce undesirable results.
Some systems use a voice activity detector to determine whether to apply echo cancellation or to gate the captured microphone signal. When the voice activity detector does not identify voice in the microphone signal, the system may gate the microphone signal to reduce the amount of noise transmitted back to the far side receiver. For some types of audio signals, the voice activity detector may help control the feedback loop problem and maintain the background noise level in the system. However, for other types of audio signals, the use of a voice activity detector may not accurately recognize the signal. In these systems, the voice activity detector may not improve the performance of the system's background noise estimator. However, when a voice activity detector is not used in some systems, a feedback loop may occur which could result in a continually growing background noise level in the system.